The complexation of carboxyl groups to metal ions was exploited to in situ prepare metal particles on the electrode surface for electrocatalysis of hydrogen peroxide (H2O2). Poly(acrylic acid) (PAA) was first electrodeposited onto a gold electrode. Then copper ions were chemically adsorbed within the PAA network, and subsequently reduced by hydrazine hydrate to yield zerovalent copper. The resultant Cu clusters were uniformly dispersed in the PAA network and their size and density could be easily controlled through controlling the amount of copper ions in the film and the loading-reduction cycles. Thus modified electrode showed good current response to H2O2 due to the catalytic activity of copper particles. Various metal catalysts can be prepared on the electrode surface by the same method. Moreover, PAA can covalently immobilize enzyme and antibody by bonding between amino groups of the biomolecules and free carboxyl groups of PAA, therefore, a variety of new chemo- and bio-sensors could be constructed.

Key words: metal particle, in situ preparation, poly(acrylic acid), H2O2, biosensor